Power plants for the generation of electrical energy based on the combustion of fossil fuels have been proposed to include plants for the capture of carbon dioxide (CO2) produced in order to reduce the emission of this gas into the atmosphere known to significantly contribute to the green house effect. Most recently, the operation of such power plants has started in pilot projects.
Known carbon capture plants include a CO2 absorber operating on the basis of chilled ammonia or amine processes and furthermore several CO2 compressors in order to compress the captured CO2, which would enable its storage and/or transport. These CO2 capture and compression processes require energy in the form of heat and steam pressure. The absorption processes require a heat source for the regeneration of the absorption agent in a heat exchanger, and the CO2 compression requires pressurized steam to drive turbines, which in turn drive compressors.
WO2008/090167 discloses a power plant with a CO2 capture and compression plant, which provides steam to drive the turbines for the CO2 compressors by extraction from a heat recovery steam generator HRSG. Further steam for this purpose is provided by the HRSG, where additional fuel is combusted in the HRSG. The low-pressure steam from the turbines driving the compressors is used for the regeneration of the absorption agent.
EP551876 discloses a power plant with CO2 capture and compression plant comprising steam lines from the high-pressure steam turbine of the power generation plant leading to turbines to drive the compressors for the compression and cooling of the captured CO2. Such use of high-pressure steam results however, in a reduction in efficiency of the power plant as a whole due to the loss of high-pressure steam in the turbines driving the generator.